Rotary fluid pumps and motors and the like



Nov. 15, 1960 K. A. @VRETVEIT ROTARY FLUID PUMPS AND MOTORS AND THE LIKE Filed April 12, 1955 5 Sheets-Sheet 1 lilllln s KARSTEN A.vReTYel7 Nov. 15, 1960 K. A. @VRETVEIT 2,960,039

ROTARY FLUID PUMPS AND MoToRs AND THE LIKE s sheets-sheet 2 Filed April 12, 1955 Nov. 15, 1960 K. A. QVRETVEIT ROTARY FLUID PUMPS AND MOTORS AND THE LKE Filed April l2, 1955 3 Sheets-Sheet 3 mrs United States Patent() ROTARY FLUlD PUMPS AND MOTORS AND THE LME Karsten Alfred vretveit, 87 Lower Road, Fetcham, England rIhis invention relates to rotary pumps.

It has been customary to make rotary fluid pumps, motors, and the like having a housing which encloses `a pumping rotor provided with pumping blades, and a sealing rotor. The pumping and sealing rotors are arranged on parallel axes in bearings and they'are geared -together to rotate in opposite directions in cylindrical compartments in the housing. Normally the pumping blades protrude axially from said pumping rotor and can enter corresponding slots in the sealing rotor without sealing contact therewith. Also said pumping blades are vin sealing engagement with said housing. All of these Vrotary pump parts are arranged so that the main torque is at all times carried by the pumping rotor in contradistinction to a Rootes type blower or a gear pump wherein "the main torque alternates between the cooperating rotors.

It has also been proposed to make rotary pumps having Va pumping rotor blade which enters a slot in the sealing Yrotor so that during each rotation of the pump the pumping rotor blade remains wholly within the periphery of the sealing rotor for a predetermined time interval whereby the volume of fluid contained in said slot remains substantially constant during this time interval.

It has furthermore been customary in sealing-rotor pumps of the kind described to make the slots in the sealing rotor large'compared to the dimensions of the blades thatthereis excessive clearance between the blades and thrust and compressed within the blade slots in the sealing rotor. This thrust originally resulted from the kinetic energy of the liquid and from the pressure which the blade exerted upon the liquid which was itself incom pressible. Normally the displaced liquid moved in a direction opposite to the main direction of the pumped Eliquid and opposed such flow with resulting decrease in the power output produced by the pump. To make flow of such displaced liquid as easy as possible it was taught .to make the clearance as large as possible but this was found to be particularly undesirable because it further limited the power of which the pump was capable. If

on the other hand an attempt was made to decrease such clearance then excessive vibration or hammer would result.

It is an object of the present invention to provide a rotary pump having a construction enabling comparativefthe building of larger pumps.

It has been proposed to provide in rotary pumps several aslots in the sealing rotor for the accommodation of the bypass.

g 2,960,039 PatentedV Nov. l5, 1960 ice blades of the pumping rotor together with limited intercommunication between the several slots so that theV hydrostatic forces acting upon the sealing rotor might be balanced. Such proposal hasalso included the teaching regarding the provision of recesses in the housing of the sealing rotor so that when the recesses are charged with uid at the correct pressure a balance of hydrostatic forces acting upon the sealing rotor is maintained. Also according to this proposal charging of the recesses is secured through small intercommunicating slots while the pumping rotor blades are entering and leaving the slots or else through small ducts communicating with the inlet and outlet ports yof the rotary pump. Such an a1- rangement for improving hydrostatic balance is employed in `certain embodiments of the present invention.

According to the present invention a rotary pump is so constructed and arranged that a substantial part of the liquid which is displaced as the pumping-rotor blades enter and leave the slots of the sealing rotor bypasses the clearances between the Iblades 'and the rims of the slots so that the whole or a substantial part of the displaced liquid does not have to pass through said clearances around the ends or sides of thefblades, It must of course be understood that the slower the speed and the larger the pump the more it becomes desirable to provide the smallest possible clearance betweenV the blade and the casing immediately adjacent to the point where the blades enter or leave the slots, and between the blades and the sealing rotor itself. Y

Consequently the phrase the rim of the sealing rotor slot as used herein includes not only the partof the sealing rotor at the edge of the slot, but also the parts of the casing which are adjacent thereto when the blades enter and leave the slot or slots.

According to anotheraspect of the present invention, the rotary pump is constructed with a small clearance between the pumping blades and the rims of the sealing rotor slots and with bypass channels-forthe liquid displaced as the blades enter and leave the slots. g ,Y

According to further aspects of the present invention, at least two slots are symmetrically disposed around the circumference of the sealing rotor and the bypass is provided through the sealing rotor to at least another of said slots and thence to the outlet or inlet of the pump as may be appropriate. It should be understood that liquid from the outlet side of the pump must be passed to the'outlet, and liquid from the inlet passed to the inlet side of the pump. Also, to obtain the full benefit of the teachings of the present invention it should be understood that the size and arrangement kof the bypass channels, and the Vdirection of the outlet or inlet where the bypass channels connect with the outlet or inlet of the pump, must be chosen to allow the free liow of liquid passing along the Referring to the` drawings:

Figure 1 is a section onV the line AB in Figure@ showing the radially liquid pressure balanced pumping rotor and sealing rotors constructed according to one form of the invention. The sealing rotors are shown in sealing position with two of the rotor blades in pumping position and the other two rotor blades in idling position.

Figure 2 is a section on the horizontal line, CD in Figure 1 showing another view of the axially liquid pressure balanced pumping rotor andv sealing rotors.

Figure 3 is a vertical section on the line EF in Figure l showing the pumping rotor blades in position in the annular pumping grooves in the pumphousing.

Figure 4 is a half section of Figure `1 showing one of the sealing rotors in one phase of the blade receiving position in the anticlockwise direction of rotation of the pumping rotor or conversely ,for blade leaving position the clockwise direction `rect axial seals for the sealing rotors. .shafts 18 and-19 are parallel with the blade rotor shaft .20

of rotation of the pumping rotor.

Figure 5 is a section showing one construction whereby metallic rotor blades are also shown lined with plastic resin.

Figure 6 is a section on the line GH in Figure 7 showing a modided embodiment of the Ainvention in which the bypass channels are differently constructed and in which the sealing rotor is solid.

Figure 7 isa section on lthe line IK in Figure 6, with the solid sealing rotors removed for clarity.

Figure 8 is a fragmentary section along part of the line GH in Figure 7 showing the rotors in a different position.

Figure 9 is a section on the line LM in Figure l() showing a further embodiment of the sealing rotor.

Figure l is a section on the line NO in Figure 9.

In lall the drawings the same reference numerals are used throughout to designate the same parts. Turning now to the embodiment shown in Figures 1 through 4 the pump housing is designated by reference numeral 1. For simplicity and rigidity the housing is made in two halves 1a and 1b which are screwed together at the face 2. In order to t the rotor axial adjustment may be obtained by the use of packing (not shownV and well known) which may be inserted between the two parts which constitute the housing.

The shaft of the pumping rotor 3 is journalled in bearings 4 in the housing 1. The rotor bearings 4 can carry both axial and radial load. The bearings are adjustable axially by adjusting rings 5 and 5a so that the rotor 3 4can run with close lit but without actual metallic Contact with the pump stator surface 6. The rotor blades 7 are rectangular in shape and protrude axially on each side on the periphery of the rotor 3. The blades are of equal length and radial width.

The rotor blades 7 are arranged to run in annular blade grooves 8 provided in both halves of the housing 1. The blade grooves have a depth and width suicient to fully receive therein the blades 7 and a close running t exists between the blades and the blade grooves.

The surfaces of the blade grooves -8 and of the main rotor shaft 20 are coaxial. Although four rotor blades are shown in this embodiment of the invention it is obvious that any desired number of rotor blades may be used.

The minimum number of rotor blades is actually determined by the seal which must be maintained throughout the rotation of the rotor between the inlet channels V10 and the outlet chanels 11. The sealing rotors 12 and 13 are placed in pairs on shafts 18 and 19 in cylindrical compartments in the housing 1 on either side of the wall 9 which is itself situated on the same plane and ush with the sides of the main rotor 3. By this arrangement the sealing rotors 12 and 13 are axially balanced.

The sides of sealing rotors 12 and 13 extend on each side 25 and 26 of the main rotor 3 and the rotor blades 7 pass into the sealing rotor blade receiving slots 21,22, 23, and 24. n

Shafts 18 and 19 are mounted in `bearings 14 and 15 in bearing holders 16 and 17 which are tightly fttedin housing 1 and axially adjustable in order to provide cor- The sealing rotor and-the three shafts are geared together by gears 33, 34,

.and 35 in a suitable manner so that the blades 7 coact in the slots 21, 22, 23, andr24.

Thus, the blades 7 enter and leave the slots 21, 22,23-, and 24 in the sealing rotors 12 and 13 as the blade rotor and the sealing rotors rotate and the blades 7 pass from the pressure side following the fully drawn arrow (Figures 1 and 4) across the inlet channel 11 via the sealing sectors `25and 26 and the slots in the sealing rotors.

The width of the blade receiving slots 21, 22,23, and

and 26 respectively to thereby prevent communicationl be- '24 is smaller than the width of the sealing sectors 25 v tween the ports 40 and 41. In order to prevent excess trapping and vacuum of the hydraulic medium .as the blades 7 move into or out-'of the slots in the sealing rotors, the sealing rotors are made hollow with passages 27 and 28 and the inlet and outlet ports 29 and 30 communicate with the inlet and outlet channels 10 and 11 of the pump respectively. The 'sealing rotor bearings are adjustable for axial and radial clearance by the end covers 31 and adjustment rings 32. The gear wheels 33, 34, and 35 run in totally enclosed compartment 36.

A seal 3-7 is provided to prevent liquid leakage from the pump housing where the pump shaft 20 extends outside the housing. A similar arrangement is shown in dotted lines 3S on the opposite side of the pump.

The fragmentary sectional View in Figure 5 shows one arrangement of metal rotor blades 7 lined with a suitable plastic resin material 7a on the `sides of the blades which might come into contact with the metallic surface in the annular blade grooves 8 in the housing 1 to prevent said annular blade grooves from being worn in case of inaccurate itting of the pump rotors in the housing 1 or due to wear in the bearings 4 and also to facilitate the provision of a minimum clearance between the blades and the annular blade grooves Without risking damaging the annular blade groove surface, whereby the maximum pumping efficiency can be obtained.

It will be understood that passages 27 and 28 -in the hollow sealing rotors 12 and 13 and the channels 29 and 3l) constitute bypass means for bypassing the liquid around the ends and sides ofthe blades 7 so that as blades 7 enter and leave the slots 21, 22, 23, and V24 a substantial portion of the liquid displaced flows along the bypass instead of around the blades whereby substantially equal liquid pressure exists on opposite sides of blades 7 in a substantially continuous manner so that hammering is prevented.

If the pumping rotor 3 rotates anticlockwise, then the pumped liquid will follow the direction shown by the fully drawn arrows, the liquid will be sucked into the pump through the channels 10, pumped out through the annular blade grooves 8, prevented from passing back to the channels 10 by the sealing rotors 12 and 13, and forced out from the pump through the outlet channels 11. In order to reduce the risk of radial unbalance of the sealing rotors 12 and 13, the ports 40 and 41 should be made as small as possible but obviously sufficient in size to permit passage of blades 7 therethrough.

As the blades 7 .pass from the ports 40 to ports 41 the corresponding peripheral slot in the sealing rotor is being moved into position by -the gear wheels 33, 34, and 35 so thatthe blades 7 can pass from port 40 to port 41 or from port 41 to port 40 without touching the slots 22, 23 or 21, 24. As the blades 7 pass the ports 40 into the slot 22, Figure 4, the pressure liquid can pass through the channels 27 and 28 in the sealing rotors 12 and 13 respectively and out from the channels 30 in the housingl Vand join up with the flow of liquid .from the channels 11 through external pipes, not shown, so that trapping of the pressure liquid in the ports 40 is avoided.

When the blades 7 move out of the slots 22 and 23 :or 21 and 24 in the sealing rotors 13 and 12 respectively and pass the ports 41, Figures l and 4, excessive vacuum'fis avoided by the fact that the neutral liquid can be sucked from the channels 29 through the channels 27 and 28 in the sealing rotors and the channels 29 are in connection with external pipes (not shown) and with the main suction channels 10. The ports 29 and 30 are rarranged diametrically and symmetrically opposite the blade ports 41 and 40 respectively. The areas of the sealing rotors 12 and V13 which are subjected to the radial pressure through the ports 40 and 30 or 29 and 41 will therefore be equal in size, The slots 21, 22, 23, and 24, on the periphery of each ofthe sealing rotors 12 and 13 respectively are also diametrically and symmetrically opposite to each other, so that the radial thrust against the sealing rotors 12 and 13 by the-pressure liquidzfroni fthe ports 40 and 30 or 29 and 41 is equalised. The sealing rotor shafts 18 and 19 are run with bearing clearance in the bores 42 and 43.

' Due to the diiculty in maintaining the main shaft seal 37 against relatively high pressure, a 'communication passage 50 and 51 betweenthe main Abearing compartments andthe gearing compartment 36 is arranged to be connectedfto an expansion tank throughthechannel 54, Figure 2, or to be connected to the suction side of the pump through the same channel 54. The expansion tank is not shownl as such was deemed unnecessary being obvious to any one skilled in the art. Normally only one end of the main pumping rotor shaft 20 has to protrude outside the housing but the main shaft 20 can be arranged to protrude outside the housing on both sides of the pump, see the dotted lines in Figure 2. A suitable shaft seal 37 may also be provided for the second shaft extension.

Axial balance of the pumping rotor in Figures 1 through 8 can further be ensured by holes 52 through the rotor 3 between -the blades 7 to communicate with the annular blade grooves 8 on both axial sides of the rotor 3 to secure equal pressure on both sides of said rotor. Thereby the risk of uneven axial thrust due to uneven flow of liquid past the edges of the blades 7 or due to uneven leakage between the rotor 3 and the pressure compartments formed by annular blade grooves S of the housing is eliminated.

Turning now to the modified embodiment shown in Figures 6 through 8, it is noted that two sealing rotors are mounted on opposite sides of the vertical axis of the housing and that these sealing rotors are not shown in Figure 7. A bypass is arranged from the idling area 60 (Figure 6) through the opening 41 (Figure 8) and a port 61 (Figure 6) in the end surface 62 of the sealing rotor compartment and out through the channel 63 into the main channel 10. In a similar way, a bypass is arranged from the main channel 11 through the channel 64, the port 65 and opening 40 (Figure 8) out into the idling space 66 (Figure 6). The part 67 (Figure 8) of the pumping rotor housing, between the ports 61 and 65, is made sufficiently wider than the width of the slots 21 and 22 in the sealing rotor 12 to facilitate sealing throughout the rotation of the sealing rotor 12.

The bypass ports 61 and 65 extend to the radial depth of the blade recesses 21 and 22 (Figure 6), and said bypass ports are so arranged that the inner portion 68 (Figure 8) is closed or opened by slots 21 or 22 before the outer portion 69.

When the blades 7 (Figure 6) pass the opening 41 and enter the slot 22, the liquid in front of the blade and the liquid displaced by the blades 7 when they enter the slot 22 are bypassed relatively freely through the port 61 and channel 63 out into the main channel 10. Thus, practically no liquid passes around the blade 7 and trapping of the liquid in the port 41 and in the slot 22 is avoided thereby preventing hammering. In a similar Way, in the opposite direction, as the blades 7 move out of the slot 22 the liquid is sucked relatively freely from the main channel through the channel 63 and out through the port 61 and fills the blade groove behind the blade 7 to thereby prevent cavitation or the formation of an excessively low pressure area behind the blade.

Figures 9 and 10 show a further embodiment constructed according to the invention wherein the hollow sealing rotor sections have sealing extensions 70 with end clearance 71 for the blades 7 in the slots 21 and 22. In this way the sealing rotor can have a wide running clearance 72 from the housing 1. The by-pass channels indicated by 29 and 30 in Figures' 9 and l0 are seen arranged as in Figures l and 4. Communication passage 73 (Figure 9) is arranged in the sealing rotor 12 and provides communication only between the slots 21 and 22 to ensure even pressure on both sides of the sealing wall 9 if uneven leakage should take place between the axial surfaces of the sealing wall 9 and the adjacent closely fitting axial surfaces of the sealing rotor 12.

In'view of the foregoing description taken in conjunction with the accompanying drawings it is believed that a clear understanding of the device will be quite apparent to those skilled in the art. It is to be understood, however, that even though there is herein shown and described several embodiments of the invention, the same is susceptible to certain further changes fully comprehended by the spirit of the'nvention'as'herein described and by the scope of the appended claims.

What is claimed is:

1. A hydraulic machine comprising a housing, a rotor in said housing, blades on said rotor, at least one chamber in said housing in which said blades operate, at least one blade always being in said chamber, at least one inlet and one outlet port in communication with said chamber, at least one inlet and one outlet channel communicating with said chamber at said inlet and outlet ports respectively, at least one sealing rotor in said housing continuously sealingly extending across the chamber between said inlet and outlet ports, at least one slot in said sealing rotor for the reception of said blades as each said blade enters and leaves said chamber passing from said Outlet port to said inlet port, said slots having dimensions sufficient to receive said blade without s'ealing with said blade, by-pass passages communicating with said inlet and outlet channels downstream of said outlet port and upstream of said inlet port and communicating `successively with said slots at least during the entry and exit of said blades into and from said slots and when said blades block communication between said ports and slots so that liquid is by-passed from a slot to said outlet channel and from said inlet channelfto said slot successively, the arrangement being such that liquid displaced by a `said blade entering a said slot flows through said by-pass from said slot to said outlet channel and liquid displaced by said blade when said blade leaves said `slot ows from said inlet channel to said slot without reversal of ow.

2. A hydraulic machine according to claim l, in which said by-pass passages include channels provided in the sealing rotor.

3. A hydraulic machine according to claim l, in which lthe said by-pass passages include channels Wholly contained in the housing.

4. A hydraulic machine according to claim 1, in which said by-pass passages include channels formed partly in the sealing rotor and partly in the housing.

5. A hydraulic machine according to claim 3, wherein said by-pass passages include channels axially disposed and extending approximately to the radial depth of the slot in the sealing rotor, said by-pass passage channels forming part of the inlet and outlet channels in the housing. l

6. A hydraulic machine according to claim 4, wherein said by-passl passages include channels axially disposed and extending approximately to the radial depth of the slot in the sealing rotor, said by-pass passage channels forming part of the inlet and outlet channels in theA housing.

7. A hydraulic machine according to claim 3, wherein the innermost end of the slot opens to at least one said by-pass passage channel before a mouth of said slot is opened to admit a blade and closes after said mouth is closed subsequent to the blade leaving said slot.

8. A hydraulic machine according to claim 4, wherein the innermost end of the slot opens to at least one said by-pass passage channel before a mouth of said slot is opened to admit a blade and closes after said mouth is closed subsequent to the blade leaving said slot.

9. A hydraulic machine according to claim 5, wherein the innermost end of the slot opens to at least one said by-pass passage channel before a mouth of said slot is opened to admit a blade and closes after said mouth is closed subsequent to the blade leaving said slot.

7 10.. A hydraulic machine according to claim 6, wherein the innermost end of the s1ot Opens toV at least one said by-pass passagercharinel4 before 'a mouth of said slot is opened to` admit a blade and closes after said mouth is closed subsequent to The blade leaving said slot.

References Cited in the-file of this patent UNITED STATES PATENTS 145,382 Baker Dec. 9, 1873 8 Marburg Mar. 16, 1897 Jaeger Aug. 13,' 1901 Marburg Nov. 7, 1905 Fagan Feb. 16, 1909 Herrick July 13, 1909 MarksV Nov. 9, 1909 Winberg May 9, 1911 Tygard July 16, 1918 FOREIGN PATENTS Germany Aug. 26, 1915 

